In apparel stores, there is a need to know products customers are interested in from information of the products picked up by the customers, for example, clothes. Then, there is known a method of attaching a radio tag having an sensor such as a vibration sensor to a product and reading information of the radio tag thereby to monitor the state of the product.
For example, the Japanese Patent Application Laid-Open No. 2004-78632 discloses a customer trend survey system having monitoring means for monitoring whether a product is moved by a customer or not by a radio tag having a vibration sensor and a counting means for counting the number of times of moving the product. Besides, the Japanese Patent Application Laid-Open No. 2006-195502 discloses of a battery-cell-less passive tag having a sensor. With this, it is possible to collect information of how much customers are interested in the unsold products.
However, in the above-mentioned system, for example, if a target cloth hanged by the hanger is picked up, adjacent products are moved to be set aside. Then, the sensor of the radio tag of the product set aside responds inevitably and it becomes difficult to know the products held by the customers only.
In addition, as such measurement is performed also when the salesclerk is in touch with a product for arrangement, and therefore, it becomes difficult to know the number of times of the customer picking up of the product.